1. Field of the Invention
The invention relates to a vacuum lifting plate for board-shaped production pieces, the vacuum lifting plate providing a vacuum chamber connected to a vacuum pump for sealing against the board-shaped production piece, and a suspension arrangement for a hoisting device.
2. The Prior Art
A small, compact vacuum lifting device for planar materials that can be fixed to a crane is described in German Patent DE-S 40 13 065. The arrangement has a vertical support structure which clasps a rod attached by an eye bolt to the crane hook. The other end of the rod is connected with a suction cushion that works together with the planar material to form a vacuum cheer. An electro-motorized suction pump is attached to a base plate on top of the suction cushion, which is connected with the support structure and connected through a vacuum opening with the vacuum chamber across a one-way ventilation return. A manually operable ventilation for interrupting the vacuum pressure is provided between the suction opening and the one-way ventilation return and the environment. When in operation, the structure fits snugly against the planar materials, whereby the ventilation for interrupting the vacuum pressure is closed. By switching on the motor switch the motor and the suction pump begin to run, so that a suction pressure results through the vacuum chamber and holds the planar material in place on the suction cushion.
In German DE-OS 38 34 866, a vacuum lifting device for planar production pieces such as boards, plates, and planks made out of wood or processed wood is described. This vacuum plate device has at least one suction plate with one or more vacuum chambers with ventilation control for the formation and release of a vacuum in each vacuum chamber. In this way each vacuum chamber is connected to the vacuum plate over a vacuum conduit that has ventilation control placed separately from the vacuum plate on the lifting device, the suction pressure of which is adjustable and the suction pressure adjustment of which can be locked. Each suction conduit is made from a flexible hose assembly connected to a fitting of the vacuum plate chamber at one end and to a straight or angled connection socket of the ventilation control at the other end.
A rubber form for vacuum cross beams for hoisting pipes is known from German DE-OS 35 10 719, whereby the rubber form is pieced endlessly together from individual sections and a rail is mounted on the base piece between two steel legs. The ventilation is largely formed so that the base piece of the section, when seen as a cross-section, consists of an indentation and that the sealing lips, facing outward, are adjacent to a trapezoidal middle section.
The known devices described above are suited to lifting even board-shaped production pieces. Production pieces whose surfaces are not even, for example, production pieces made of corrugated steel, trapezoidal corrugated sheets or similar materials, are not easily lifted with the known lifting devices.
The object of the present invention is to provide a vacuum lifting plate which can lift not only even production pieces, but also production pieces with uneven surfaces which extend in more than one direction, for example, corrugated or trapezoidal corrugated surfaces.